Mechanism for effecting smooth starting of a hydraulic motor



2 Sheets-Sheet 1 D. F. PRICE Aprii 4, 1961 MECHANISM F'OR EFFECTING SMOOTH STARTING OF A HYDRAULIC MOTOR Filed Feb. 23. 1956 lNvENToR Do/VALD FI PRICE TTORNEY ,mpi 1 VIII/[lll April 4, 1961 D, F, PRICE 2,977;933

MECHANISM FOR EFFECTING SMOOTH STARTING OF' A HYDRAULIC MOTOR Filed Feb. 25, 1956 2 Sheets-Sheet 2 lNvENToR .va/wlw EPR/c5 ATTORNEY United States Patent MECHANISM FOR EFFECTING SMOOTH STAl-R'Ii-V ING OF A HYDRAULIC MOTOR Donald F. Price, Waynesboro, Pa., assignor to Landis Tool Company, Waynesboro, Pa.`

Filed Feb. 23, 1956, Ser. No. 567,188 `11 Claims. (Cl. 121-441) has been that in overcoming starting friction of a WorkA carriage, for example, pressure would build up tothe point necessary to overcome the friction, then the carriage would lurch a short distance before settling down to the speed for which the mechanism was adjusted. No satisfactory solution has been found to this problem although air bleeders have provided a slight improvement. This condition has been tolerated because until recently, it has had no objectionable effect on the grinding operation. However, with the advent of new grinding methods, particularly the plunge and traverse method in which the grinding wheel is fed in the full depth of cut and then the traverse movement started, the lurching start has resulted in damage to the grinding wheel.

It is, therefore, an object of this invention to provide means for controlling the start of a Vhydraulic traverse mechanism.

A further object is to provide means for opposing the `traverse movement and then gradually reducingV the force of opposition.

A further object is to provide a valve for blocking the ow of exhaust lluid from a traverse motor and for thereafter shifting the valve at a controlled rate to permit a gradual release of the exhaust fluid.

Fig. l shows a sectional hydraulic diagram of the traverse motor and the control valve; Y Y

Fig. 2 is thesame as Fig. l except thatsome of the valve members are in different positions. Y t

Numeral 10 indicates a hydraulic cylinder. A divided piston 11 is slidably mounted in cylinder 10. Piston rods 12 and 13 passingthrough the ends of cylinder 10 are secured to bed 2.0 of a machine tool bysuitable brackets 21. Cylinder 10 is attachedto and movable with work carriage 17.

Fluid under pressure is directed through passage 14 in pistonv rod 12 and throughpassage 15in piston rod 13. Air bleeders 16 are provided at each end of cylinder 10. Fluid under pressure is supplied to passage 14 through line 22 and to passage 15 through line 23. Each line 22 and 23 is supplied with Huid from reversing valve 24.

Lands 25 and 2-6 of reversing valve 24 are tapered so that at each reversal, the change in direction of uid flow and therefore, in the direction of traverse, is effected smoothly. The start and stop valve 30 has a land portion `31 which, in the left hand or start position shown in Figure 2, connects line 71 with reversing valve 24 in order to direct fluid under pressure to cylinder 10. At the same time, exhaust passage 73, which is connected to the left end of valve 40, is connected by valve 30 Vwith exhaust outlet port 74. Valve 40 is, therefore, free to move to the left under the power of spring 41 `to block the by-pass between ports 42. i

An intermediate portion 62 has a tapered left end for` effecting a gradual enlargement of the passage between ports 78 and 79.

Valve portions 61 and 62 are mounted in a large bore 90. A small portion 63 at the right end of valve 60 is mounted in a small bore 91. Passage 64 extends axially through valve 60 from radial passage 65 which opens into an elongated port 66 connected to port 67.

A spring pressed ball check valve 68 in passage 64 operates in the position shown of valve 60 to admit fluid under pressure from port 67 and from passage 65 into passage 64. The purpose of valve 68 is to permit the passage of Huid under pumppressure through passage 64 to reset valve 60 to the left when valve 30 is in right hand or stop position as-shown in Figure 1.

When Valve 30 is in the left hand or start position, exhaust passage 73 is connected by land portion 31 with port 74, port 78 and line 80 with the left end of valve 60. Exhaust fluid is permitted `to move valve 60 to the right at a rate determined by the discharge of fluid from bore 91through passage 75 under the control of throttle valve S6 to effect a gradual enlargement of the passage between ports V78 and 79 with a corresponding increase inthe rate of movement of the movable member.

Operation With the start and stop Valve 30 in right hand or stop position, as shown in Figure l, fluid under pressure from pump 70 passes through line 71 and port 72 in valve 30 through port 67, port 66 in valve 60, passages 65 and 64 and passage which is blocked by land 76 of valve 30. Port 66 is long enough that it is connected to passage65 in valve 60 regardless of whether valve 66 is in left o1 right hand position. Pressure is, therefore, built up against small portion 63 of valve 60, and either moves it to the left or holds it in the left hand position depending on its position when pump 70 is started. In the left hand position of valve 60 shown, the flow of exhaust lluid from port 78 to port 79 is prevented by the tapered intermediate portion 62 of valve 60.

Fluid from port 72 also passes through port 67 and exhaust passage 73 since land 31 on valve 30 cuts olf exhaust outlet port 74. From exhaust passage 73, fluid is directed to the left end of valve 4t), shifting valve 40 to the right against spring 41 and connecting ports 43 and 44 through ports 42-so that uid under pressure is supplied simultaneously to both ends of cylinder 10 through lines 22V and 23 to provide the same force acting on carriage 17 during manual traverse operations as during power traverse operations. s

When valve 30 is in the right hand or stop position, land portion 31 connects both reversing valve 24 and exhaust passage 73 with line 71. Pressure in exhaust passage 73 shifts valve 40 to the right against spring 41 and connects ports 42 to by-pass fluid from one side of cylinder 10 to the other. At the same time, tluidfrom line 71 is directed to port 45 of reversing valve 24 from which it is distributed to one of the ports 43 or 44 depending on the position of reversing valve 24.

Assuming that valve 24 is in the position shown in Figure 2, uid from port 45 is directed through line 22.

nected to line 71. Fluid passing through passage 73 toy the left end of valve 40 shifts valve 40 to the right to con` i neet ports 42. At the same time, uid under pressure enters port 45 of valve 24 from which it is directed through port 43 and line 22 to one end of cylinder 10 and from port 43 through ports 42 and port 44 through line 23 to the opposite side of cylinderl 1t) so that pump pressure Vis maintained in both ends of cylinder 10.

When valve Si) is set for manual traverse, that is, in right hand or stop position as described above, it continues to direct lluid to valve 24 as when set for power traverse. This arrangement provides for maintaining the same forces acting on carriage 17 during manual traverse as during power transverse and thus assures uniform grinding action in both cases.

When valve 30 is shifted to the left, port 67 is connected 4to exhaust port 74 and pressure on the left end of valve 40 is relieved, permitting valve 40 to be moved by spring 41 to the left and blocking the connections between ports 43 and 44 so that fluid cannot ow freely' from one side of cylinder to the other.

Assuming that valve 24 is in the left hand position, iluid under pressure from port 45 will be directed through port 43, line 22 to the left end of cylinder 10 to shift cylinder 10 and carriage 17 to the left. At the same time, iluid will be exhausted from the right hand end of cylinder 10 through line 23, ports 44 and 5S and line 56 to traverse speed control throttle valve 94. When carriage 17 reaches the end of Ithe stroke to the left, it acts through suitable connections to shift valve 24 to the right.

When valve 24 is in the right hand position, ilu-id under pressure from port 45 is directed through port 44 and line 23 to the right end of cylinder 10 to shift cylinder 10 and carriage 17 to the right. Exhaust fluid from the other side of cylinder 10 will pass through line 22, port 43, passage 120 in valve 24, and exhaust port 55 which serves both ports 43 and 44 through line 56 and valve 94.

Whether valve 24 is in right or left position, exhaust iluid from valve 94 passes through passages 57 and 73 to port 67 in valve 30 and through port 74 in valve 30 to port 78 in valve 60. After valve 60 has moved to the right, exhaust fluid flows from port 78 through port 79 to the tank. Since valve 60 is in position to prevent the passage of exhaust fluid to exhaust outlet port 79, said exhaust iluid is directed through line 80 to the left end of valve 60 to shift valve 60 to the right. Since valve 30 has moved to 4the left (Figure 2) to starting position, land 76 has opened up passage 75 through throttle valve 86 to outlet port 79 so that valve 60 may move to the right at a rate determined by the setting of throttle valve 86. In moving to the right, intermediate portion 62 of valve 60 provides a progressively increasing opening between ports 78 and 79 so that any tendency of carriage 17 to lurch is prevented by the resistance to ilow of the of the exhaust fluid between ports 78 and 79. As valve 60 continues to move to the right, this resistance is progressively reduced so that carriage 17 eventually moves at the rate for which valve 94 is set.

The operation of valve 60 is not effected at each reversal, but only when start and stop valve 30 is shifted from left hand or start position to right hand or stop position.

I claim:

l. In a hydraulic system having a connection for fluid under pressure and a connection for exhaust iluid, means for controlling the discharge of exhaust fluid comprising a valve having a large area end and a small area end, intermediate inlet and discharge ports and a tapered portion for permitting or preventing the llow of exhaust luid between said ports, a supply of fluid under pressure for said hydraulic system, means for directing said iiuid under pressure to the small area end of said valve to shift said valve to prevent the passage of fluid between said ports, means including a passage connecting said discharge port to the large area end of said valve to direct exhaust uid to shift said valve in the opposite `direction to connect said ports to permit the discharge of said exhaust lluid, and means for adjusting the rate of movement of said valve comprising an adjustable restriction for controlling the discharge of fluid from said small area end of said valve.

2. In a hydraulic system, a reciprocable motor, a supply of fluid under pressure for driving said motor, a reversing mechanism for directing fluid alternately to opposite sides of said motor, a start and stop valve for controlling the supply of tluid to said reversing mechanism, a passage for conducting exhaust fluid from said reversing mechanism, a pressure operated valve normally blocking said exhaust passage, said start and stop valve having means operable, when in stop position, for directing fluid under pressure to hold said pressure operated valve in blocking position and having means operable, when in start position, for directing exhaust fluid to shift said pressure operated valve in a direction to open said exhaust passage.

3. In a hydraulic system, a reciprocable motor, a supply of fluid under pressure therefore, a reversing mechanism for directing fluid alternately to opposite sides of said hydraulic motor, a start and stop valve for controlling the supply of fluid to said reversing mechanism, an exhaust line from said reversing mechanism to a reservoir, a pressure operated exhaust valve having axially spaced inlet and discharge ports, said valve having a large area end, a small area end, and a intermedite portion. said intermediate portion separating said axially spaced ports in said exhaust valve, an exhaust passage from said small area end having a throttle valve therein for regulating the flow of said exhaust fluid, means on said start and stop valve for blocking the flow of exhaust fluid from said small area end when said start and stop valve is in right hand or stop position, connections between said start and stop valve in the stop position for directing fluid under pressure to said small area end of said exhaust valve, blocking of-said exhaust passage causing said fluid to shift said valve to the left to prevent the flow of exhaust fluid from said reversing mechanism, connections between said start and stop valve in the start position for directing exhaust fluid through said first mentioned connections to the small area end of the exhaust valve, a connection from one of said axially spaced ports to the large area end of said exhaust valve, said start and stop valve in start position acting to unblock the exhaust passage from said small area end whereby said exhaust valve may move under the pressure on said large area end to connect said spaced ports at a rate determined by the setting of said throttle valve.

4. In a hydraulic system, a reciprocable motor, a supply of fluid under pressure therefore, a reversing mechanism for directing tluid alternately to opposite sides of said hydraulic motor, an exhaust passage for conducting exhaust fluid from said motor, a start and stop valve for controlling the supply of fluid to said reversing mechanism, a pressure operated valve normally blocking said exhaust passage and having a large area end and a small area end, means to direct exhaust fluid from said motor to one end of said pressure operated valve, an exhaust line from the other end of said pressure operated valve, a restriction in said exhaust line to control the movement of said pressure operated valve in response to the exhaust pressure at the other end thereof, and means in said pressure operated valve for gradually opening said exhaust passage.

5. In a hydraulic system including a fluid motor, a source of fluid under pressure, a start and stop valve for controlling said supply of fluid under pressure to said motor, an exhaust line in said hydraulic system for discharging said tluid from said motor, a valve in said exhaust line for controlling the speed of said motor, a pressure operated blocking valve in said exhaust line, said blocking valve being operable in one position for preventing l'the discharge of said exhaust fluid, and connecposition to direct exhaust fluid to shift said blocking valve,

to open position.

6. In a hydraulic sy'stem including a lluid motor, a source of fluid under pressure, a start and stop valve for controlling said supply of fluid under pressure to said motor, an exhaust line in said hydraulic system for discharging said lluid from said motor, a valve in said exhaust line for controlling the speed of said motor, a pressure operated blocking valve in said exhaust line, said blocking valve being operable in one position for preventing the discharge of said exhaust fluid, connections between said blocking valve and said start and stop valve operable when said start and stop valve is in left hand or start position to direct said exhaust lluid to shift said blocking valve to open position, and connections between said blocking valve and said start and stop valve when said start and stop valve is in right hand or stop position for directing fluid under pump pressure to shift said blocking valve to said right hand or stop position for preventing discharge of exhaust iluid.

7. In a hydraulic system, a reciprocable motor, a supply of fluid under pressure for driving saidmotor, a reversing mechanism for directing Huid alternately to opposite sides of said motor, a start and stop valve for controlling the supply of fluid to said reversing mechanism,

' a by-pass valve and connections from said start and stop valve when said start and stop valve is in stop position for directing fluid under pressure to shift said by-pass valve to connect opposite sides of said motor.

8. In a hydraulic system, a reciprocable motor, a sup- Y ply of fluid under pressure for driving said motor, a reversing mechanism for directing lluid alternately to opposite sides of said motor, a start and stop valve for controlling the supply of fluid to said reversing mechanism, a by-pass valve, a spring for actuating said by-pass valve in one direction, and connections from said start and stop valve to the end of said by-pass valve to exhaust the actuating iluid from said by-pass valve when said start and stop valve is shifted to prevent iluid from passing from one side ofsaid motor to the other when said start and stop valve is in start position,

9'. Inv a hydraulicl system, av reciprocable motor, a supply of fluid under pressure for driving said motor, a re- Vversing mechanism for directing fluid alternately to opposite sides of said motor, a start and stop valve for controlling the supply of liuid to said reversing mechanism,

a by-pass valve, conduits from said start and stop valve to said reversing mechanism and said by-pass valve, said start and stop valve being arranged to direct fluid under pressure through both conduits when said start and stop valve is in stop position and to connect said reversing mechanism with fluid under pressure and said by-pass valve with exhaust when said star-t and stop valve is in start position.

10. In a hydraulic system, a reciprocable motor, a supply of liuid under pressure for driving said motor, a reversing mechanism for directing lluid alternately to opposite sides of said motor, a start and stop valve for controlling the supply of lluid to said reversing mechanism, said start and stop valve being arranged to supply iluid under pressure to said reversing mechanism in both positions of said start and stop valve.

11. In a hydraulic system, a reciprocable motor, a supply of fluid under pressure for driving said motor, a reversing mechanism for directing fluid alternately to opposite sides of said motor, a start,` and stop valve for controlling the supply of fluid to said reversing mechanism, a by-pass valve, said start and stop valve being arranged when in start position to supply fluid under pressure to said reversing mechanism, and when in stop position to actuate said by-pass valve to supply fluid under pressure to both sides of said reciprocable motor.

References Cited in the le of this patent UNITED STATES PATENTS 1,605,250 MacKenzie Nov. 2, 1926 2,219,967 Thiry Oct. 29, 1940 '2,249,343 Balsiger July 15, 1941 2,328,979 Herman Sept, 7, 1943 2,477,669 Stephens Aug 2, 1949 2,782,598 Gatwood Feb. 26, 1957 

